With respect to a technique for displaying colors in the display unit of a portable information device, Japanese Patent Laid-Open No. 213799/1998 discloses a technique relating to a reflection type color display produced by a color filter system having auxiliary illumination. Japanese Patent Laid-Open No. 106328/1998 discloses a technique relating to a liquid crystal display unit for both reflection and transmission using a reflecting layer having a light polarizing state maintaining property. Japanese Patent Laid-Open No. 19257/1993 discloses a technique relating to a field sequential color system operating as a color display system in which no color filter is required. Japanese Patent Laid-Open No. 10529/2000 discloses a technique relating to a liquid crystal color display driving method in which red, green and blue liquid crystal element operating signals are synthesized and set to a monochromatic video signal on the basis of a consumed power restraining command signal, and power consumption is reduced by displaying only this monochromatic image.
As mentioned above, high image quality, color and low power consumption are required in a portable information device, but many problems, which are described below, exist in the display technique employed by the conventional color portable information device.